package editor.cn;

//反转一个单链表。 
//
// 示例: 
//
// 输入: 1->2->3->4->5->NULL
//输出: 5->4->3->2->1->NULL 
//
// 进阶: 
//你可以迭代或递归地反转链表。你能否用两种方法解决这道题？ 
// Related Topics 链表 
// 👍 1421 👎 0

import java.util.List;

public class ReverseLinkedList{
    public static void main(String[] args) {
        Solution solution = new ReverseLinkedList().new Solution();
        ListNode listNode01 = new ListNode(1);
        ListNode listNode02= new ListNode(2);
        ListNode listNode03 = new ListNode(3);
        ListNode listNode04 = new ListNode(4);
        ListNode listNode05 = new ListNode(5);
        listNode01.next = listNode02;
        listNode02.next = listNode03;
        listNode03.next = listNode04;
        listNode04.next = listNode05;
        solution.reverseList(listNode01);
    }

//leetcode submit region begin(Prohibit modification and deletion)
/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode reverseList(ListNode head) {
        ListNode dummy = new ListNode(0);
        dummy.next = head;
        while (head != null && head.next != null) {
            ListNode dnext = dummy.next;
            ListNode hnext =head.next;
            dummy.next = head.next;
            head.next = head.next.next;
            hnext.next = dnext;
        }
        return dummy.next;
    }
}
//leetcode submit region end(Prohibit modification and deletion)

}
 class ListNode {
    int val;
    ListNode next;
    ListNode(int x) { val = x; }
}
